δ¹⁵N

δ¹⁵N (delta-15 N) refers to the ratio of two stable nitrogen isotopes: ¹⁵N:¹⁴N. Each contains seven protons with the former containing eight neutrons and the latter, seven neutrons. δ¹⁵N analysis, also referred to as isotopic signature, can be used to illuminate past and present climatic conditions and to provide further information for source attribution efforts. It plays an important role in agriculture and soil science, hydrology, ocean science, and paleoclimatology research applications.

For example, with climate as a primary driver of the nitrogen cycle, δ¹⁵N levels in foliage have been directly correlated to mean annual temperature and show an inverse relationship with mean annual precipitation. δ¹⁵N soil values have also been positively correlated with aridity. Other studies have explored the use of δ¹⁵N values for source attribution in agriculture, for example, to identify the type and amount of fertilizer used or to examine nitrogen sources of groundwater contamination.

Picarro has designed and produced two isotope analyzers that precisely measure δ¹⁵N in nitrous oxide for laboratory and field studies.